Coil of reference fiber for downhole fiber sensing measurement

Abstract

A method may include receiving interrogation data from a sensing fiber via a coil of reference fiber of a same type of fiber as the sensing fiber. The sensing fiber may be coupled in series with the coil of reference fiber. The method may also include receiving a known temperature and a known strain from the coil of reference fiber and outputting the known temperature, the known strain, and the interrogation data for use in calibrating a measurement of the interrogation data.

What is claimed is: 
     
         1 . A method comprising:
 receiving interrogation data from a sensing fiber via a coil of reference fiber of a same type of fiber as the sensing fiber, the sensing fiber coupled in series with the coil of reference fiber;   receiving a known temperature and a known strain from the coil of reference fiber; and   outputting the known temperature, the known strain, and the interrogation data for use in calibrating a measurement of the interrogation data.   
     
     
         2 . The method of  claim 1 , wherein outputting the known temperature, the known strain, and the interrogation data includes using an interrogator device to formulate a calibration command and output a calibration of the interrogation data. 
     
     
         3 . The method of  claim 1 , wherein the sensing fiber is spliced with at least one circulator for steering backscattered light unidirectionally between one or more inputs and one or more outputs of the at least one circulator for a portion of the sensing fiber. 
     
     
         4 . The method of  claim 3 , wherein the coil of reference fiber is coupled between the sensing fiber and the at least one circulator. 
     
     
         5 . The method of  claim 1 , wherein a Raman pump amplifier is spliced with a fiber in line with a circulator that selectively amplifies light propagating to the sensing fiber or amplifies backscattered light originating from the sensing fiber, and provides gain of the interrogation data. 
     
     
         6 . The method of  claim 1 , wherein the coil of reference fiber is coupled to one or more materials with the known temperature, the one or more materials including known properties, and wherein the known strain is a function of temperature.